Frederick VIII (Christian Frederik Vilhelm Carl) (3 June 1843 – 14 May 1912) was King of Denmark from 1906 to 1912.

Before his accession to the throne at age 62, he served as crown prince for 42 years. During the long reign of his father, King Christian IX, he was largely excluded from influence and political power.

In 1853, his father was chosen as the heir presumptive to the Danish throne, because Frederick's mother, Louise of Hesse-Kassel, was a close relative of the last Danish king of the Oldenburg main line (the other heirs of the House of Hesse renounced their claims to the Danish throne in favour of Louise and her husband). Accordingly, Frederick became a Prince of Denmark in 1853.

Crown Prince Frederick in military uniform ca. 1863-1868.

After his confirmation in 1860, Frederick was given a military education. In 1863, Prince Frederick was sent to do studies at the University of Oxford but when his father ascended the throne in November that year, he became Crown Prince and returned to Denmark.

As Crown Prince of Denmark, he was given a seat in the State Council and subsequently assisted his father in the duties of government.

Louise of Hesse wanted her eldest son to marry as well as her two daughters, Alexandra and Dagmar, had. Queen Victoria of the United Kingdom had two yet unmarried daughters, Princess Helena and Princess Louise, and Louise tried to marry Frederick to one of them. However, the British Queen didn't want her daughters to marry the heirs to foreign crowns, as this would force them to live abroad. She preferred German princes who could establish homes in the UK. In addition, Victoria had always been pro-German and another Danish alliance (Frederick's sister, Alexandra, had married Victoria's eldest son, the Prince of Wales), would not have been in line with her German interests.

The marriage was suggested as a way of creating friendship between Denmark and Sweden. The two countries were in a tense situation after Sweden had not assisted Denmark during the war with Prussia in 1864. Frederick and Louise had met for the first time in 1862, but in 1868 Frederick was invited to Sweden to get to know Louise, and their meeting was described as a success. They became engaged the same year. She was the first Swedish princess to be married into the Danish royal house since the Middle Ages, and the marriage was welcomed in all three Scandinavian countries as a symbol of the new Scandinavism.

Frederick became king of Denmark as Frederick VIII on Christian IX's death on 29 January 1906. He was 62 years old at the time and had been Crown Prince for 43 years.

In many ways Frederick VIII was a liberal ruler who was much more favorable to the new parliamentarian system than his father had been. Because of his very late accession to the throne he had only a few years to show his ability and he was weakened by ill health.

On his return journey from a trip to Nice, King Frederick made a short stop in Hamburg, staying at the Hotel Hamburger Hof. The evening of his arrival on 14 May 1912, Frederick (incognito) took a walk on the Jungfernstieg. While walking he became faint and collapsed on a park bench and died. He was discovered by a police officer who took him to a Hafen hospital where he was pronounced dead. His cause of death was announced as a paralysis-attack. He was interred with other members of the Danish royal family in Roskilde Cathedral near Copenhagen.

The royal families of Denmark, Norway, Belgium and Luxembourg are descended from King Frederick VIII. Denmark comes naturally, Norway's family goes through the line of his son, Prince Carl, and the families of Belgium and Luxembourg are descended from his daughter, Princess Ingeborg of Denmark.

Princes that lost their title following an unequal marriage are shown in italics
^Not a Danish prince by birth, but created a prince of Denmark
*Also a prince of Greece ∞Also a prince of the United Kingdom ‡Also a Count of Monpezat